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Shuttle holds up on return

There are no obvious signs that re-entry worsened damage around a gouge.

By CURTIS KRUEGER, Times Staff Writer
Published August 22, 2007

The Space Shuttle Endeavour returns safely to the Kennedy Space Center at the end of a 13-day mission to the International Space Station. The shuttle's thermal protection system survived re-entry as engineers had predicted.

CAPE CANAVERAL -- This time, seven astronauts plunging through searing heat as they re-entered Earth's atmosphere knew they were riding a damaged space shuttle.

This time, unlike the 2003 Columbia disaster that killed an entire crew, NASA managers had scrutinized the defect, studied it and declared it manageable.

This time, all seven astronauts landed safely at Kennedy Space Center.

"I've got to tell you, I breathe a sigh of relief every time we have a successful launch and a successful landing," NASA administrator Michael Griffin said Tuesday. "Anyone who doesn't understand that in the truest sense of the word this is an experimental vehicle is just not getting it."

The astronauts were beaming at a news conference Tuesday evening. Even former teacher Barbara Morgan, feeling woozy after the landing, was smiling. Five hours after landing, she said, "the room still spins a little bit," but she was enthusiastic about the future of space exploration.

The safe landing of Endeavour on Tuesday was a mixture of triumph and trouble for NASA.

It left the space agency's top administrators confident they had made the right call by deciding not to repair the hole on the spacecraft's protective thermal skin. The gouge was caused by insulating foam that fell during launch, the same thing that doomed the crew of Columbia.

But at the same time, this mission is a reminder that the space shuttle design ensures the falling foam problem will occur again and again, as long as Endeavour,Atlantis and Discovery continue to fly.

"I think we will continue to lose foam. ... I think we'll still expect to see some things come off, and we'll have to analyze them," said NASA associate administrator Bill Gerstenmaier.

Said Griffin: "On every flight we seem to have some interesting question that has to be resolved, or certainly it's a rare flight where we don't. And I expect that to continue."

After the landing Tuesday, Griffin and Gerstenmaier made a quick inspection of the hole in the 1.1-inch-thick thermal tile. They saw no evidence that the heat of re-entry had seriously worsened the damage, although the hole did appear somewhat larger. Workers will continue inspecting it to see if it damaged the shuttle's aluminum structure, underneath the tiles.

The space shuttle's giant orange external tank is coated with some 4,000 pounds of insulating foam to prevent ice from coating the tank. Why would ice form in the Florida heat? Because the fuels inside that tank are stored at minus 297 and minus 423 degrees.

This Styrofoam-like coating looks and feels harmless, but at the supersonic speeds of the shuttle launch, a small detached chunk can cause big damage. The chunk that gouged Columbia's left wing and destroyed the craft was about 1.7 pounds, the size of a laptop.

After Columbia, NASA devised a robotic arm fitted with a laser and camera that checks for damage in hard-to-see areas. This inspection process is what revealed the hole in a protective tile on Endeavour's underbelly. Space shuttles have suffered this kind of foam damage even before Columbia, but because there was no in-flight inspection, no one saw it until the shuttles landed.

During Endeavour's flight, NASA for the first time used a high-tech modeling system that allowed engineers to replicate the damaged tile on Earth. Data from the laser inspection was transmitted back to NASA, which fed the information into a three-dimensional printer. This printer works like a regular two-dimensional computer printer but builds one layer on top of another, creating a solid, 3-D replica.

That replica was used in various tests on Earth to determine the effect of the estimated 2,000-degree heat that the damaged tile would encounter during re-entry. These tests were a big part of the reason NASA decided the hole was not going to destroy Endeavour.

Commander Scott Kelly said those tests gave him absolute confidence his craft was safe.

Asked if the tile damage weighed on his mind, Kelly said: "To be honest with you, it crossed my mind for a moment and only in the sense that I knew I was going to be asked about it. I didn't worry about it at all. I mean, when we were informed of the type of testing and analysis that was going on and the rigor and the time that was put into it to make the right decision based on the data, I was as certain as I could be about anything that it wasn't going to be an issue."

NASA officials also are studying a possible redesign of some brackets on the external tank, hoping to reduce some of the falling foam. A redesign would likely delay the next space shuttle launch, scheduled for October.

For Morgan, the former teacher, the space flight came after decades of waiting. She had been the backup to Christa McAuliffe, the teacher-in-space who was killed during the 1986 Challenger launch explosion.

Morgan said she felt "a great sense of pride"' to be helping with the endeavor of space exploration. She said she had enjoyed the opportunity to answer students' questions while in space, and that she was looking forward to sharing more with students in the future.